Switchable optical vortex beam generator based on an all-dielectric metasurface governed by merging bound states in the continuum

The polarization topology around the bound states in continuum (BIC) affects the optical vortex (OV) beam generation. We propose a cross-cross-shaped resonator based on a THz metasurface to realize an OV beam generator in real space by exploiting the inherent winding topology around the BIC. The BIC merging at the point & UGamma; is achieved by tuning the width of the cross resonator, which significantly improves the Q factor and enhances the field localization. Furthermore, the switching between the high-order OV beam generator governed by the merged BIC and the low-order OV beam generator is realized. This extends the application of BIC in modulating orbital angular momentum. & COPY; 2023 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement

Automated summary

This paper presents a cross-cross-shaped resonator based on a THz metasurface to generate an optical vortex (OV) beam in real space. By exploiting the polarization topology around the bound states in continuum (BIC), the merging of BIC at the point & UGamma; is achieved by tuning the width of the cross resonator, which improves the Q factor and enhances field localization. Moreover, the switching between high-order and low-order OV beam generator controlled by the merged BIC is realized, extending the application of BIC in modulating orbital angular momentum.